1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same.
2. Description of the Related Art
It is remarkable that various kinds of portable electronic machinery and tools have come into fairly wide use so quickly in recent years, and they would be more widely used day by day and year by year. In compliance with such a trend, the semiconductor device of the resin sealed type to be fitted to the portable electronic apparatus has been required to have a configuration which is thinner in thickness, smaller in size and lighter in weight. In order to comply with such requirement, there has been proposed a chip size packaged (CSP) semiconductor device as a high-densely fabricated semiconductor device.
An advanced semiconductor device generally includes several different semiconductor elements or devices respectively playing different roles, for instance a role of executing the memory processing, a role of performing the logic processing and so forth. Accordingly, the condition for manufacturing these different semiconductor elements or devices has to be naturally changed based on their different roles and functions. However, it would be difficult in general to provide a single semiconductor element or device with such different roles and functions. In order to obviate this difficulty, the following way has been taken so far, that is, separately manufacturing semiconductor elements or devices with respect to every necessary function, and then organizing semiconductor elements or devices having different functions by packaging them on a single printed board. However, in case of packaging a plurality of separately manufactured semiconductor elements or devices on a single printed board, there arises a problem that the number of semiconductor elements or devices which are allowed to be packaged on one surface of the printed board has to be naturally limited, in other words, the desirable high-density packaging is made difficult or rather impossible.
In order to solve this problem, there has been proposed a structure which is completed for instance by puffing one semiconductor element on the other, connecting the wiring formed on respective semiconductor elements with each other by means of thin metal wires, and finally applying a sealing resin to the entirety of the piled-up and connected semiconductor elements to cover it therewith. According to the structure like this, the high-density packaging might be made possible without increasing the size or the surface area of the printed board. However, another problem arises in connection with the total manufacturing yield of the semiconductor device as a finished product. In general, the semiconductor elements receive a simple test for checking their performance in the state of their being in a wafer. On the other hand, the more complete final test (i.e. shipping test) is carried out with regard to only a semiconductor device in which semiconductor elements have been fabricated. Consequently, if the semiconductor device is assembled by using two semiconductor elements which have not yet passed the final test, the final manufacturing yield of the semiconductor device as a finished product is given as the product of respective manufacturing yields with respect to two semiconductor elements. Consequently, the manufacturing yield would drop in reverse proportion to the degree of packaging density of the semiconductor device, which leads to the increase in the manufacturing cost.